1. Field of the Invention
The present invention relates to an electrical contact assembly, and more particularly, to a composite contact assembly having lower contact with contact engaging points offset from each other thus establishing reliable electrical connection between the lower contact and a mating upper contact.
2. Description of the Prior Art
Burn-in Socket is widely used for testing an IC package, so as to detect performance of the IC package and distinguish defective IC packages. A typical Burn-in Socket generally comprises an insulative housing having a number of electrical contact assemblies received therein. The electrical contact assembly generally comprises an upper contact, a lower contact and a spring between the upper contact and the lower contact. The upper contact comprises a flat base portion with a first contact portion at the top end. The lower contact comprises a flat body portion and a pair of arm portions extending upwardly from the body portion. The bottom end of the body portion has a second contact portion. The base portion is sandwiched between arms and the arms can move along the base portion.
When the CPU presses the upper contact, the upper contact moves downwardly and presses the spring, the arms moves along the base portion of the upper contact and contacts with the base portion all along. When the CPU is removed, the elastic force of the spring will push the upper contact moved upwardly to the initial stage.
The pair of arm portions each has a contacting point for engaging with the base portion and will exert a retaining force on the base portion. The pair of arm portions has equal length such that provides equal torque on the upper contact. Thus, electrical connection between the upper contact and the lower contact will be established. In order to ensure the arm portions moving along the base portion freely, said retaining force is needed to be controlled in a predetermined range. However, the retaining force will be reduced if the contact assembly is used in some worse application and the electrical connection between the upper contact and lower contact will be affected.
In view of the above, a new electrical contact that overcomes the above-mentioned disadvantages is desired.